Algorithms for Parity Games

Abstract

It is the aim of this chapter to review some of the algorithmic approaches to the problem of computing winning strategies (resp. of deciding if a player has a winning strategy from a given vertex) in parity games with finite arenas and other two-player games. Parity games are equivalent via linear time reductions to the problem of modal μ-calculus model checking (see Chapters 10 and 9), and this model checking problem plays a major role in computer-aided verification. Furthermore we will see that the problem is not too hard in a complexity-theoretic sense, while no efficient algorithm for it is known so far. Also parity games are the simplest of a whole chain of two-player games for which no efficient solutions are known, further underlining the importance of looking for an efficient algorithm solving this particular problem.